This invention relates to a transmission chain adjuster for motorcycles and more particularly to an improved, simplified and compact chain adjusting mechanism for the drive of a wheeled vehicle.
In many types of wheeled vehicles, such as motorcycles, chain transmisions are still very popular and practical as a manner for driving the wheels. Even though the driven wheel may be supported for suspension travel such as by a trailing arm arrangement, there are numerous advantages to the use of a chain drive transmission. Recently, however, it has been proposed to provide a very wide, low pressure rear wheel for motorcycles that will facilitate off the road use. In addition, the wheel is also supported for suspension movement by a trailing arm construction. With this type of device, it is practical to use a pair of driving chains for driving the rear wheel. The first chain extends from the engine output shaft to an idler shaft and is disposed close to the longitudinal center line of the vehicle. The second chain is driven by the idler shaft and, in turn, drives the rear wheel and is positioned laterally outwardly a sufficient distance so as to permit such drive for the rear wheel. The advantage of such two chain constructions is that the first chain can be positioned close to the center line and in a location where it will not interfere with the rider's legs. An example of such an arrangement is shown in Japanese Utility Model Publication No. 54-35470.
With the use of such a dual chain arrangement, however, there are certain difficulties in connection with the chain placement and its adjustment. For example, in the aforenoted Japanese utility model publication, the axis of rotation of the idler shaft is disposed coincident with the pivotal axis of the trailing arm. This gives rise to the use of a very short primary driving chain and substantially increases the stresses on the chain. In addition, it is necessary or desirable to provide some arrangement for permitting adjustment of the chain tension and the placement of the type shown in that utility model application makes it very difficult to obtain sufficient width for adjusting of the chains.
It is, therefore, a principal object of this invention to provide an improved transmission mechanism for motorcycles.
It is another object of this invention to provide an improved motorcycle transmission mechanism wherein the tensioning of the drive chains can be easily facilitated.
It is a yet further object of this invention to provide an improved and compact, yet easily adjusted, chain drive transmission mechanism for motorcycles.